The present invention relates to a substrate transport method and apparatus for transporting a substrate to a processing section to clean the surface of the substrate, and also relates to a substrate processing system having the substrate transport apparatus.
In a photolithographic process of manufacturing the semiconductor devices, it is very important to maintain the surface of the wafer clean. This is because if contaminants, such as particles, organic substances, and metallic ions, are attached to the surface of the semiconductor wafer, they significantly defect a circuit pattern of the semiconductor device. Therefore, in the photolithographic process, the wafer surface is usually washed when necessary. The contaminants are removed from the wafer surface, for example, by rubbing the wafer surface by a brush while a chemical washing solution is poured thereon. Such a washing treatment is usually carried out in a washing apparatus equipped with a spin chuck and a rotatory brush.
As shown in FIG. 1, a conventionally used substrate processing system 100 has a processing section 104 for washing the surface of the wafer with a chemical solution and drying it, and a substrate transporting arm mechanism 105 for transporting the wafer W to the processing section 104. The processing section 104 has three processing units 101, 102, 103. The substrate transport apparatus 105 has three arms 106a, 106b, 106c. The processing units 101, 102, 103 have loading/unloading ports 101a, 102a, 103a, respectively. The wafer W is loaded/unloaded into/from units 101, 102, 103 through the loading/unloading ports 101a, 102a, 103a, respectively.
The substrate transport apparatus 105 has an X-axis driving mechanism for moving an arm portion 106 in an X-axis direction, a Z-axis driving mechanism 107 for moving the arm portion 106 in a Z-axis direction, a .theta.-axis driving mechanism for rotating the arm portion 106 around the Z-axis, and a back-and-forth moving mechanism for moving each of arms 106a, 106b, 106c back and forth. The Z-axis driving mechanism 107 has a single ball screw 110 whose rotation movement is driven by a motor 109. The motor 109 and the ball screw 110 are surrounded by a cover 108 in the expandable bellows form.
However, when the Z-axis driving mechanism 107 is used for a long time, particles are sometimes generated from the cover 108 in the form of bellows, attaching onto the wafer W.
Furthermore, as shown in FIG. 2, the vertical opening length of the loading/unloading port 101a in the conventional apparatus is larger than the vertical size of an assembly of three arms 106a, 106b, 106c. Thus, the particles are likely to enter the processing unit 101 when the wafer W is loaded/unloaded. In addition, a shutter 130 is moved in a long distance and thus long time is required to open/shut the loading/unloading port 101a. As a result, throughput of the treatment decreases. Furthermore, it take long time to exchange the first arm 106a arranged at the uppermost stage and the third arm 106c arranged at the lowermost stage, with the result that the throughput decreases.